Lankesteriana International Journal on Orchidology ISSN: 1409-3871 [email protected] Universidad de Costa Rica Costa Rica Tupac Otero, Joel; Mosquera, Ana Teresa; Flanagan, Nicola S. TROPICAL ORCHID MYCORRHIZAE: POTENTIAL APPLICATIONS IN ORCHID CONSERVATION, COMMERCIALIZATION, AND BEYOND Lankesteriana International Journal on Orchidology, vol. 13, núm. 1-2, agosto, 2013, pp. 57-63 Universidad de Costa Rica Cartago, Costa Rica Available in: http://www.redalyc.org/articulo.oa?id=44340043007 How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative LANKESTERIANA 13(1–2): 57—63. 2013. TROPICAL ORCHID MYCORRHIZAE: POTENTIAL APPLICATIONS IN ORCHID CONSERVATION, COMMERCIALIZATION, AND BEYOND JOEL TUpaC OTERO1, 2*, ANA TERESA MOSQUERA3 & NICOLA S. FLANAGAN3 1Departamento de Ciencias Biológicas, Universidad Nacional de Colombia sede Palmira, Cra 32 12-00, Palmira, Valle del Cauca, Caolombia 2Instituto de Estudios Ambientales IDEA, Universidad Nacional de Colombia sede Palmira, Colombia 3Programa de Biología, Pontificia Universidad Javeriana, Cali, Colombia *Author for correspondence: [email protected] ABSTRACT. Orchid mycorrhizae are unique interactions in the plant kingdom involving all the orchids and a variety of fungi including Rhizoctonia. Orchids are one of the most charismatic plant families and include at least 20,000 species widely appreciated by specialist growers and scientists. They also include Vanilla, source of one of the most traded spices worldwide. Most mycorrhizal fungi belong to a group of basidiomycetes widely known for their pathogenic interaction with many crop plants including potatoes, rice, and beans. The main application of orchid mycorrhizal fungi is in the propagation of endangered and commercial orchid species, but we have recently documented an alternative use. The fungal symbionts of orchids have the ability to induce resistance to Rhizoctonia in rice plants, which opens new possibilities of biological control agents never previously imagined. KEY WORDS: mycorrhiza, fungi, Orchidaceae, Rhizoctonia, biological control Comprising 10% of angiosperm species, that and other countries grow and export species native Orchidaceae contains an estimated 25,000 different to the Neotropics. Orchid commercialization is also species (Dressler 1993). Within Ecuador, 3784 orchid a growing industry in Neotropical countries. While species are reported, with 3264 species in neighboring many, if not most, orchid commercialization ventures Colombia (Dodson 2003). The high diversity of are based on the sustainable propagation of plants ex Orchidaceae in these countries reflects the presence of situ, the novelty value of rare endemic species (which two biodiversity hotspots in the northwestern region are often difficult or impossible to cultivate) means of South America: the tropical Andean region and these species are subjected to continuing collection the Chocó-Darien biodiversity hotspot (Myers et al. pressures. Additionally, currently non-commercialized 2002). species may provide valuable genetic resources in the Orchids have attracted considerable scientific development of novel commercial hybrids. It is not interest since Darwin`s seminal publication (1877). without reason that the whole of Orchidaceae with Unfortunately, the fascinating and diverse floral the exception of artificially propagated hybrids in morphology of orchids has also led in recent the genera Cymbidium, Dendrobium, Phalaenopsis, decades to serious threats to the survival of many and Vanda has been placed on Appendix II of the orchid species. Particularly in regions with weak Convention on International Trade in Endangered law-enforcement, considerable pressure is exerted Species of Wild Fauna & Flora (CITES), which lists on natural orchid populations from unsustainable species that are not necessarily now threatened with extraction of specimens from their natural populations extinction but that may become so unless trade is for commercialization. The value of ornamental trade closely controlled. in orchids has been estimated at US $2 billion annually Compounding the negative impact of wild (Harron et al. 2007). The ornamental orchid market specimen collection on orchid populations is the fact in Taiwan alone was reported to be valued at US that many orchid species tend to be rare in the wild, $114 million in 2012. Although the Taiwan industry often with small, hyper-dispersed populations. This is is largely based on Phalaenopsis species, breeders in particularly true for epiphytic species, which comprise 58 LANKESTERIANA an estimated 70% of all orchid species (Zotz, in press), species (Taylor & Bruns 1997; Selosse & Roy 2009). with the great majority of these species occurring in In tropical taxa, studies of epiphytic orchids in tropical regions. In addition to extraction pressures, Oncidiinae have also revealed moderate to high levels many orchid populations also face challenges to of preference for specific clades of Ceratobasidium their survival from habitat destruction and ecosystem spp. (Otero et al. 2002, 2004, 2007; Valadares et al. degradation, effects that are likely to be exacerbated 2012). More recently, Martos et al. (2012) showed a as a consequence of their specialized interactions general pattern for different fungal preferences among with pollinators, phorophytes, and mycorrhizal fungi. orchids with terrestrial and epiphytic habits on the Furthermore, a recent study indicates that other, as yet island of Réunion. unidentified factors related to microhabitat conditions Although historically the greater focus has been may be limiting orchid distribution and abundances placed on orchid pollination biology, it is likely (McCormick et al. 2012). There is clearly much we that seedling establishment, rather than seed set, is still have to learn regarding orchid biology in natural the limiting step in orchid life cycles (Calvo 1993; habitats, in particular for tropical species, in order to Otero & Flanagan 2006; Tremblay & Otero 2009). understand the evolutionary processes underlying One pollination event will yield millions of seeds the high species diversity in this plant family and that are generally wind-dispersed. Seed germination also identify factors that determine distributions and and seedling establishment, in contrast, may be abundances of orchids in the wild so as to develop more challenging for the orchid plant. Lacking effective conservation strategies for them. endosperm, orchid seeds have minimal energy The combination of commercial interest in tropical resources for germination and rely instead upon orchids and the rapid rate of ecosystem degradation mycorrhizal symbioses to provide carbon and nutrients in tropical regions has led to dramatic declines in (Bidartondo et al. 2004; Selosse & Roy 2009). Thus many orchid populations (Seaton 2007). Among many the availability of a suitable mycorrhizal fungus conservation measures that need to be implemented, is crucial to orchid establishment in the wild, and key requisites for ensuring orchid population survival studies of orchid mycorrhizae across the family have are the maintenance of the levels of recruitment of yielded a complicated panorama of orchid mycorrhizal individuals into established populations as well as the associations with varying degrees of specificity to one restoration of orchid populations in suitable sites. or several different fungal taxa (e.g. Otero et al. 2002; Orchid research has principally focused on Martos et al. 2012). taxonomy and the role played by pollination biology Orchid mycorrhizal interactions also occur in in diversification (Micheneau et al. 2009; Schiestl adult plants. In photosynthetic plants it has been & Schluter 2009). However, other aspects of their generally assumed that the provision of carbon to the biology, in particular their mycorrhizal interactions, plant from the fungus is not essential, yet it seems are increasingly gaining prominence in the scientific that mixotrophic nutritional strategies, in which the literature (e.g. Rasmussen 1995; Dearnaley 2007; plant receives carbon from both photosynthesis and Kottke & Suarez 2009; Hossain et al. 2013). In addition mycorrhizal interaction, are common (Selosse & Roy to the specialized relationships orchids often have with 2009; Roy et al. 2013). In this case it may be that their pollinators, accumulating studies have revealed different parts of the plant receive carbon provision that some epiphytic orchids may also have strong from both sources. There is some indication that those preferences for their host tree (phorophyte) as well fungi involved in seed germination are not the same as as their associated mycorrhizal fungi. Clear examples those that associate with adult plants. In tests of seed of orchid distributions being limited with respect germination efficiency of different fungal isolates from to phorophyte have been reported (e.g. Gowland adult plants, fungi with provenance from other species et al. 2007, 2013; Crain 2012). Varying degrees of were sometimes more efficient (Otero et al. 2004; mycorrhizal specificity have been observed throughout Porras & Bayman, 2007). Orchidaceae (Kottke et al. 2009; Yuang et al. 2010; Generally, mycorrhizal fungi in orchids belong Valadares et al. 2012), in particular in achlorophyllous to the Rhizoctonia-like